Pipe fitting

ABSTRACT

A compression pipe fitting is provided. The fitting comprises a body defining one or more sockets for receiving an end of a pipe, a clamping nut and a grip ring. The socket is encircled by a threaded face, and is internally adapted to receive a compressible O-ring. The nut can be screwed onto the threaded face of the socket and has an internal tapered surface while the grip ring has a complimentally tapered surface which, when the nut is tightened onto the threaded face, bears upon the grip ring compressing it against the pipe and compressing the o-ring located within the socket.

RELATED APPLICATIONS

This is a continuation of U.S. national stage application Ser. No.13/810,142, filed on Mar. 19, 2013, which claims priority under 35U.S.C. §371 to International Patent Application No.: PCT/ZA2011/000020filed on Jul. 7, 2011, which claims priority to South African PatentApplication No. 2010/04923 filed on Jul. 13, 2010, the disclosures ofwhich are incorporated by reference herein their entireties.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a pipe coupling and in particular a push-fitcompression fitting.

BACKGROUND ART

Prior art pipe fittings are available which act as either compressionfittings or push-fit fittings, but not both.

For example, JP 2001074178 (Bridgestone Corp), which aims to reduce thenumber of parts constituting a pipe joint, is a push-fit fitting but isnot a compression fitting. This fitting includes a grip ring (1) whichcomprises a cylinder/ring made of resin, with a number of metallic clawsor teeth embedded in the ring such that the tips of the teeth protrudeto engage the pipe that is fitted. A cap (15) screws onto the pipe body(11) but does not act on the grip ring (1). The cap simply retains theO-ring in place and prevents it from moving under pressure, but does notcompress the O-ring and therefore does not act as a compression fitting.This is clear from FIGS. 5, 6 and 7 of the patent.

CN 201237049 (PRIORITY DATE Oct. 7, 2008)

This is a utility model (registered design) for a quick pipe joint for acompressed air pipe. The pipe joint comprises a joint pipe (1) (seedrawings) and a press cover (2) detachably connected to the joint pipeby means of a screw thread. A clamp ring base (5) is arranged on thehead section of the joint pipe. The inner end of the clamp ring (5)protrudes into the joint pipe. A sealing ring (4) abuts against theclamp ring base (5). The inner ring of the sealing ring protrudes(stands proud) out of the inner diameter of the clamp ring base. A metalelastic clamp ring (6) is arranged at the outer end face of the clampring base (5) and includes a ring body and claw teeth folded in thedirection of the clamp ring base. A bevel ring is arranged at theopening of the clamp ring base and the claw teeth about the bevel ring.A pusher (7) abuts the outer end of the elastic clamp ring and a boss(on the press cover 2) abuts the other end of the pusher.

In use, the press cover (2) is screwed tightly and the boss on the presscover causes the pusher to drive the elastic clamp ring (6) against thebevel ring, causing the teeth to “expand” and clamp the pipe.

Although the pusher acts against the clamp ring to expand the teeth andclamp the pipe, and therefore allows it to act as a push-fit fitting, itdoes not engage the O-ring at all. This is clear from FIG. 1 that theclamp ring base 5 engages and abuts against the end of the joint pipe 1which prevents the clamp ring base acting upon the O-ring 4.Accordingly, and although the O-ring may protrude into the innerdiameter of the clamp ring base, it simply acts as a seal and is notcompressed about the compressed air pipe. The fitting of CN 201237049therefore is a push-fit fitting but not a compression fitting or apush-fit compression fitting.

It is an object of this invention to provide a push-fit pipe couplingwhich has the additional advantage of including a nut which may betightened thereover to provide additional gripping force and bettersealing.

DISCLOSURE OF THE INVENTION

According to the invention, a push-fit compression pipe fittingcomprises a body defining one or more socket for receiving an end of apipe, the socket being encircled by a threaded face; and beinginternally adapted to receive a compressible O-ring; a clamping nutwhich can be screwed onto the threaded face, and a grip ring; the nuthaving an internal tapered surface and the grip ring having acomplimentally tapered surface which when the nut is tightened onto thethreaded face, bears upon the grip ring compressing it against the pipeand compressing the O-ring sealing means located within the socketagainst the pipe.

The socket includes a circumferential recess about the mouth thereofwhich acts as an O-ring seat; and a rear shoulder or flange or step.

The grip ring preferably comprises a split ring which preferably has aninternal diameter which is slightly smaller than the external diameterof the inserted pipe, which results in the grip ring expanding slightlywhen the pipe is inserted therethrough. The grip ring further includes aplurality of small teeth spaced apart about the internal or pipeengaging surface thereof. In the preferred form, the grip ring comprisesa stainless steel ring embedded within a plastic composite material. Thestainless steel ring includes about its internal diameter, one or moreteeth angled inwardly and in the direction of the fitting body when thefitting is assembled.

The underside of the grip ring is dimensioned to engage the mouth of thesocket, and may include a ridge or the like protruding formationdefining a stepped surface adapted to engage the O-ring, the ridge beingspaced apart from the external diameter of the grip ring to fit withinthe O-ring seat and linearly compress the washer and O-ring, against theO-ring seat, causing the O-ring to be deformed and in so doing tightlyengaging the inserted pipe end. The ridge may be eliminated by providingan o-ring having a larger cross sectional diameter.

In the preferred form of the invention, a flat washer may be providedbetween the O-ring and the grip ring. The washer may be omitted, asdescribed above with the grip ring engaging the O-ring directly, but thefitting has been found to perform better under extreme pressureconditions if the washer is present, as it prevents damage to the O-ringcaused by the ends of the split ring under these conditions.

Because the internal diameter of the grip ring is smaller than that ofthe external diameter of the inserted pipe, the fitting acts as apush-fit compression fitting, expanding the grip ring as it pushestherethrough with the result that full tightening of the clamping nutmay not be required. However, when the clamping nut is tightened, thereis a force opposing that exerted by the nut on the grip ring, whichresults in a tight engagement between not only the pipe and grip ring,but especially between the O-ring and the pipe. This is particularlyuseful where the pipe is scratched or damaged and additional compressionis required.

Thus it is the grip-ring which prevents the pipe from being pulled outof the fitting, but it is the O-ring which provides significantcompression resulting in a unique push-fit compression fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiment of the invention is described below withreference to the accompanying drawings in which:

FIG. 1 is a sectional view through a pipe coupling of the invention inoperational condition,

FIG. 2 is a sectional isometric view through the coupling of FIG. 1,

FIG. 3 is sectional view of a coupling pipe removed and clamping nutdisengaged,

FIG. 4 is the same view as FIG. 3 but with the clamping nut engaged,

FIG. 5 is a sectional side view of a grip ring,

FIG. 6 is a plan view of the grip ring of FIG. 5,

FIG. 7 is an isometric from below of the grip ring,

FIG. 8 is a sectional side view of the stainless steel split ring,

FIG. 9 is a plan view of the split ring of FIG. 8, And

FIG. 10 is an isometric view from below of the split ring of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIGS. 1 to 4, a pipe fitting or coupling 10 comprises a body 12, aclamping nut 14, a grip ring 16 and a washer 18 and an O-ring 20.

The body 12 includes a socket at each end for receiving a pipe 22 andthe socket includes a widened recess 24 which acts as a seat for thewasher 18 and O-ring 20. Externally, the socket is threaded (FIG. 2) toreceive the clamping nut 14. Opposing sockets are separated by a flange26 or step 26.

The clamping nut 14 has an internal tapered surface 28 for engaging andbearing upon the complimentally tapered surface 30 of the grip ring 16.

The washer 18 is flat and comprises metal while the O-ring 20 comprisesa resiliently deformable material, for example rubber or siliconerubber.

Turning now to FIGS. 5 through 7, the grip ring 16 is shown to bemoulded from plastic and includes embedded therein, a stainless steelsplit ring 32 as shown in FIGS. 8 to 10. The underside of the grip ringhas a diameter sufficiently large to span the mouth of the socket andabut surface 34. The underside of the grip ring is further stepped orridged 36 at an external diameter dimensioned to fit within the recessor O-ring seat 24. This enables the ridge or step 36 to engage thewasher 28 and exert a linear force onto the washer 18 and in turn, theO-ring 20 when the clamping nut 14 is tightened.

The split ring 32 has teeth or the like protrusions 38 about itsinternal diameter, which are directed inwardly and in the direction ofinsertion of the pipe. Formations 40 and 42 assist in stabilising thestainless steel ring within the mould during moulding of the grip ring16.

In use, the fitting of the invention is pre-assembled with the clampingnut partially threaded onto the body, and the grip ring in looseabutment with both the internal tapered surface of the clamping nut andthe mouth 34 of the body. A pipe end is then pushed into the fitting,causing expansion of the split grip ring into firm abutment with thetapered surface of the nut and the mouth 34 of the body. This in turncauses linear compression of the O-ring which deforms to tightly engagethe pipe (as shown in FIG. 2). If additional compression is required,the nut may be advanced by rotation on the threaded face of the body toapply additional pressure on the grip ring and the O-ring.

1. A push-fit compression pipe fitting comprising a body defining one ormore sockets for receiving an end of a pipe, the socket being encircledby a threaded face; a clamping nut which can be screwed onto thethreaded face, and a grip ring, wherein the socket is internally adaptedto receive a compressible O-ring; the nut has an internal taperedsurface and the grip ring has a complementally tapered surface which,when the nut is tightened onto the threaded face, bears upon the gripring compressing the grip ring against the pipe and compressing theO-ring located within the socket against the pipe.
 2. A push-fitcompression pipe fitting as claimed in claim 1, wherein the socketincludes a circumferential recess about the mouth thereof which acts asan O-ring seat; and a rear shoulder or flange or step.
 3. A push-fitcompression pipe fitting as claimed claim 1, wherein the grip ringcomprises a split ring which has an internal diameter which is slightlysmaller than the external diameter of the inserted pipe, which resultsin the grip ring expanding slightly when the pipe is insertedtherethrough.
 4. A push-fit compression pipe fitting as claimed in claim1, wherein the grip ring includes a plurality of small teeth spacedapart about the internal or pipe engaging surface thereof.
 5. A push-fitcompression pipe fitting as claimed in claim 1, wherein the grip ringcomprises a stainless steel split ring embedded within a plasticcomposite material.
 6. A push-fit compression pipe fitting as claimed inclaim 5, wherein the stainless steel ring includes about its internaldiameter, one or more teeth angled inwardly and in the direction of thefitting body when the fitting is assembled.
 7. A push-fit compressionpipe fitting as claimed in claim 1, wherein the underside of the gripring is dimensioned to engage the mouth of the socket.
 8. A push-fitcompression pipe fitting as claimed in claim 7, wherein the underside ofthe grip ring includes a ridge or the like protruding formation defininga stepped surface adapted to engage the O-ring.
 9. A push-fitcompression pipe fitting as claimed in claim 1, wherein a flat washer isprovided between the O-ring and the grip ring.
 10. A push-fitcompression pipe fitting as claimed in claim 9, wherein the ridge isspaced apart from the external diameter of the grip ring to fit withinthe O-ring seat and linearly compress the washer and O-ring, against theO-ring seat, causing the O-ring to be deformed and in so doing tightlyengaging the inserted pipe end.
 11. A push-fit compression pipe fittingas claimed in claim 7, wherein an O-ring having a greater crosssectional diameter is used, replacing the need for the ridge.